The polyphenylene ether resins are a family of engineering thermoplastics that are well known to the polymer art. These polymers may be made by a variety of catalytic and non-catalytic processes from the corresponding phenols or reactive derivatives thereof. By way of illustration, certain of the polyphenylene ethers are disclosed in Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875, and in Stamatoff, U.S. Pat. Nos. 3,257,357 and 3,256,358. In the Hay patents, the polyphenylene ethers are prepared by an oxidative coupling reaction comprising passing any oxygen-containing gas through a reaction solution of a phenol and a metal-amine complex catalyst. Other disclosures relating to processes for preparing polyphenylene ethers reins, including graft copolymers of polyphenylene ethers with styrene type compounds, are found in Fox, U.S. Pat. No. 3,356,761; Sumitomo, U.K. Pat. No. 1,291,609; Bussink, et al., U.S. Pat. No. 3,337,892; Blanchard, et al., U.S. Pat. No. 3,219,626; Laakso, et al., U.S. Pat. No. 3,342,892; Borman, U.S. Pat. No. 3,344,116; Hori, et al., U.S. Pat. No. 3,384,619; Faurote, et al. U.S. Pat. No. 3,440,217; and Cooper, et al., U.S. Pat. No. 3,661,848, U.S. Pat. No. 3,733,299 U.S. Pat. No. 3,838,102, and U.S. Pat. No. 3,988,297. Dislosures relating to metal based catalysts which do not include amines, are known from patents such as Wieden, et al., U.S. Pat. No. 3,442,885 (copper-amidines); Nakashio, et al., U.S. Pat. No. 3,573,257 (metal-alcholate or -phenolate); Kobyashi, et al., U.S. Pat. No. 3,445,880 (cobalt cheltates); and the like. In the Stamatoff patent, the polyphenylene ethers are produced by reacting the corresponding phenolate ion with an initiator, such as peroxy acid salt, and acid peroxide, a hypohalite, and the like, in the presence of a complexing agent. Disclosures relating to non-catalytic processes, such as oxidation with lead oxide, silver oxide, etc., are described in Price, et al., U.S. Pat. No. 3,383,212. Cizek, U.S. Pat. No. 3,383,435 discloses polyphenylene ether-styrene resin compositions. All of the above-mentioned disclosures are incorporated by reference.
In the prior art, rubber-modified styrene resins have been admixed with polyphenylene ether resins to form compositions that have modified properties. The Cizek patent, U.S. Pat. No. 3,383,435, discloses rubber-modified styrene resin-polyphenylene ether resin compositions wherein the rubber component is of the unsaturated type such as polymers and copolymers of butadiene. The physical properties of these compositions are such that it appears that many of the properties of the styrene resins have been upgraded, while the moldability of the polyphenylene ethers are improved.
Nakashio, et al. U.S. Pat. No. 3,658,945 discloses that from 0.5 to 15% by weight of an EPDM-modified styrene resin may be used to upgrade the impact strength of polyphenylene ether resins. In Cooper, et al., U.S. Pat. No. 3,943,191 it is disclosed that when the highly unsaturated rubber used in compositions of the type disclosed by Cizek, it replaced with EPDM rubber that has a low degree of residual unsaturation, the thermal oxidative stability and color stability are improved. The EPDM rubber in the Cooper, et al. compositions is comprised substantially of particles in the range of 3-8 microns. The disclosures of the Nakashio, et al. and Cooper, et al. patents are incorporated herein by reference.
The impact strength of the Cooper, et al. compositions is superior to that of a polyphenylene ether resin alone or that of similar compositions comprised of unmodified polystyrene; however, the impact strength of the Cooper, et al. compositions is inferior to that of similar compositions comprised of polystyrene modified with polybutadiene rubber, such as a composition known as FG-834, available from Foster-Grant Co.
As is disclosed in Abolins, et al., U.S. Pat. No. 3,981,841, the impact strength of the Cooper, et al. compositions can be improved by incorporating therein impact modifiers such as an emulsion-grafted EPDM polystyrene copolymer. In copending U.S. patent application Ser. No. 787,253, filed Apr. 13, 1977, incorporated herein by reference, it is disclosed that a composition of a polyphenylene ether resin and an alkenyl aromatic resin modified with an EPDM rubber comprised of particles having a median diameter less than about two microns, preferably about 0.5 to 1.5 microns, is a very useful thermoplastic molding material having good thermal oxidative stability and good impact strength.
In copending U.S. application Ser. No. 855,250 filed Nov. 28, 1977, it is disclosed that a composition of a polyphenylene ether resin, an alkenyl aromatic resin modified with a small-particle EPDM rubber, and a hydrogenated elastomeric block copolymer is a very useful thermoplastic molding material having good thermal oxidative stability and surprisingly high impact resistance. The above application is incorporated herein by reference.
Many plastic applications require a metal-plated surface. The metal coating may be applied to provide decoration, to provide resistance to ultraviolet radiation, to provide electric conductivity, or for one of many other purposes. Plastics containing unsaturated rubber are plated by first exposing them to an etching solution, and then the surface is "activated" by deposition of a small amount of a metal, usually silver, platinum, palladium or gold. The metal thus deposited serves as a catalytic agent in the next step, the electroless plating of the surface with a continuous thin film of nickel or copper. Plating is completed by conventional electroplating methods to produce the desired plate thickness and final surface coat.
Etching is the key to successful plating of plastics. The etching solution, usually chromic acid or a solution of chromic acid in sulfuric acid, attacks the double bonds in the rubber particles, dissolving out the rubber particles and producing a surface containing many tiny undercut "holes". The partially oxidized inner surface of the holes provides a preferential site for deposition of the activating metal. This assures complete filling of the undercut holes with metal and provides the mechanical lock of the metal to the plastic which is necessary for adequate adhesion.
It has now been found that although the double bonds believed necessary for etching and adhesion are absent, compositions based on polyphenylene ether resins and saturated rubber-modified alkenyl aromatic resins can be successfully plated under standard plating conditions. The plated materials have the improved stability characteristic of polyphenylene ether resin compositions containing a saturated rubber and have surface appearance and plate adhersion, i.e., peel strength, characteristics as good as those of plated polyphenylene ether resin compositions materials containing polybutadiene or other unsaturated rubbers.
It is, therefore, a primary object of this invention to provide plated compositions that are based on polyphenylene ether resins, modified alkenyl aromatic resins, and hydrogenated elastomeric block copolymers.
Another object of this invention is to provide plated compositions and molded articles that are based on a polyphenylene ether resin and a small-particle EPDM-modified alkenyl aromatic resin and that have improved thermal oxidative stability.
Still another object of this invention is to provide plated compositions and molded articles that are based on a polyphenylene ether resin, a small-particle EPDM-modified alkenyl aromatic resin, a hydrogenated elastomeric block copolymer and that have improved strength.
It is also an object of this invention to provide the above-described, plated compositions in reinforced and/or flame-retardant embodiments.